Gear Drive Cams
Seasoned HDF Member
Joined: Dec 2005
Posts: 19,958
Likes: 8,050
From: poway
PO had installed 510g cams in my '09 which he had upgraded to a 103ci. Love them for the most part but I know its not the best choice. Around 45k miles at the moment. My question for you is if I wanted to change them could I just go with different gear cams or would they have to be from S&S? And if all is running well should the crank runout be rechecked before a different cam install?
Once you've paid the price for gears, why go back? Maybe in 200,000 miles when the are worn out?
Seasoned HDF Member
Joined: Dec 2005
Posts: 19,958
Likes: 8,050
From: poway
so do you know by chance what i need to check to make sure they work like they should. Im guessing the inside gears would be the same diameter & number of teeth to spin evenly, And the outer could be different (but no idea why)the cams would spin faster or slower than the crank
By design, the cam needs to spin at excatly 1/2 the crank and the front cam spins at the same speed as the rear. No changing that.
The inner gears have the same number of teeth always but one may be the slightest bit larger or smaller to set gear lash. The issue is the same on EVOs but set at assembly at the factory.
Again on the outers the number of teeth don't change. It's always 2 crank to 1 cam but the pinion might be slightly larger or smaller to correct for slight tolerances in spacing between the pinion and rear cam. Technically it's not an issue as far as function goes unless too tight. Too loose and they rattle.
Stellar HDF Member
Joined: Jun 2018
Posts: 2,235
Likes: 1,210
From: AZ
Yes it runs very well I just see that the 510g is more for an 88, 85 & 96. And it starts coming on well after 3000. I'd like something with the power range lower like the 551, 570 or 583. Just curious as I'm usually an 'if it ain't broke' kinda guy. Just wondering if its a big undertaking or if I could just swap the cams themselves & she'd be really to roll? The PO did all of this before I bought it, not sure why he went with the 510 cams.
Seasoned HDF Member
Joined: Dec 2005
Posts: 19,958
Likes: 8,050
From: poway
Yes, no, maybe, but the glitch is most that run gear drive, tend to go with cams that have higher RPM ranges, so means that crank is going to have more run out over time, where tight spots may not stay at 0+, but start bind to cause problems instead.
So .003" run out or less of the crank is kind of the standard, since even if it does grow slightly, should still be good.
And just a note, but on some of the twin cam factory motors from the factory, the run out was so bad, that HD change to .012" run out on the crank,: was still be in spec.
So .003" run out or less of the crank is kind of the standard, since even if it does grow slightly, should still be good.
And just a note, but on some of the twin cam factory motors from the factory, the run out was so bad, that HD change to .012" run out on the crank,: was still be in spec.
Thanks
By design, the cam needs to spin at excatly 1/2 the crank and the front cam spins at the same speed as the rear. No changing that.
The inner gears have the same number of teeth always but one may be the slightest bit larger or smaller to set gear lash. The issue is the same on EVOs but set at assembly at the factory.
Again on the outers the number of teeth don't change. It's always 2 crank to 1 cam but the pinion might be slightly larger or smaller to correct for slight tolerances in spacing between the pinion and rear cam. Technically it's not an issue as far as function goes unless too tight. Too loose and they rattle.
The inner gears have the same number of teeth always but one may be the slightest bit larger or smaller to set gear lash. The issue is the same on EVOs but set at assembly at the factory.
Again on the outers the number of teeth don't change. It's always 2 crank to 1 cam but the pinion might be slightly larger or smaller to correct for slight tolerances in spacing between the pinion and rear cam. Technically it's not an issue as far as function goes unless too tight. Too loose and they rattle.
Seasoned HDF Member
Joined: Mar 2021
Posts: 18,536
Likes: 3,745
From: backwoods
I did check gear lash when I installed mine. But talking to an S&S dealer, he was like when they first came it was only one size. He was like it will just whine Now that was 2006, maybe people are more concerned now, Either way I was ok on lash. 55k miles later.
Seasoned HDF Member
Joined: Dec 2010
Posts: 7,736
Likes: 1,524
From: Coromandel Peninsula New Zealand
Don't get hung up on crank runout but ensure that you have +0 lash on the two tight spots on the crank gear as it rotates. You may need to try a different gear pinion to do this, but I have fitted a couple of gear drive sets on bikes with "excessive runout". Both are still going well, 5 years later.
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Road Captain
Joined: Oct 2018
Posts: 539
Likes: 284
From: Coldstream B.C. CA.
I had gear timed on the 88 with 551 cams until the crap HD crank started to fail, now running a 4.375 S&S crank in the same case and bored jugs to 3.875 making it a 103. About 40,000 miles and it's still rock solid. I love gear timed!
Seasoned HDF Member
Joined: Mar 2010
Posts: 21,139
Likes: 7,653
From: Poolville
Going to gear drive is an important step in building a performance motor. Motors with chain drive terms to lag the camshaft to the crank position which can decrease the power a little bit, so I have been told.
I have considered gear drive for my Dyna but at 005" I don't think it would be a good choice to do at this time. I do have a set of S&S wheels and if I ever need to put them in, at that time I will go gear drive...
I have considered gear drive for my Dyna but at 005" I don't think it would be a good choice to do at this time. I do have a set of S&S wheels and if I ever need to put them in, at that time I will go gear drive...
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